SHIELDING ANALYSIS FOR THE ITER DIVERTOR AND VACUUM-PUMPING DUCTS

Three-dimensional shielding analysis has been performed for the ITER o utline design presented to TAC-4 in January 1994. The average neutron wall loading in ITER is 0.913 MW m(-2) for the nominal 1500 MW fusion power. The peak outboard and inboard neutron wall loadings are 1.193 a nd 0.923 MW m(-2) respectively. The divertor modules along with the va cuum vessel provide adequate shielding for the toroidal field (TF) coi ls in the divertor region. The walls of the horizontal divertor ducts are completely out of the direct line of sight of source neutrons. The contribution to total nuclear heating from streaming into the 24 dive rtor ducts is only 0.21 kW without additional duct shielding. No separ ate divertor duct shielding is needed and the duct wall 20 cm thick al ong with the mechanical structure 11 cm thick will provide adequate pr otection for the TF coils against streaming radiation. The values of t otal nuclear heating in the TF coils are only 4.14 and 4.79 kW for the stainless steel-water blanket-shield and Li-V breeding-blanket design s respectively.